In the field of medical technology and diagnostics, a large number of devices and methods for determining the presence and/or the concentration of one or more analytes in samples, specifically fluid samples, such as body fluids, and/or for determining at least one parameter of a sample are known. Without restricting the scope of the present disclosure, in the following, mainly reference is made to the determination of coagulation parameters or analyte concentrations in blood samples, e.g., to the determination of blood glucose or ketone body concentrations. As an example, reference may be made to commercially available devices and systems, such as the ACCU-CHEK® INFORM systems, the COAGUCHEK® systems or the REFLOTRON® systems, all by Roche Diagnostics GmbH, Germany. It shall be noted, however, that other types of samples or other types of analytes or parameters may be used in a similar way.
For performing fast and simple measurements, several types of test elements are known, which mainly are based on the use of one or more test chemicals, i.e., on the use of one or more chemical substances, one or more chemical compounds or one or more chemical mixtures, adapted for performing a detection reaction for detecting the analyte or determining the parameter. The test chemical often is also referred to as a test substance, a test reagent, a test chemistry or as a detector substance. For details of potential test chemicals and test elements comprising such test chemicals, which may also be used within the present disclosure, reference may be made to J. Hoenes et al.: The Technology Behind Glucose Meters: Test Strips, Diabetes Technology & Therapeutics, Vol. 10, Supplement 1, 2008, S-10 to S-26. Other types of test elements and/or test substances are feasible and may be used within the present disclosure.
By using one or more test chemicals, a detection reaction may be initiated, the course of which depends on the presence and/or the concentration of the at least one analyte or on the parameter to be determined. The detection reaction preferably may be analyte-specific. Typically, as may also be the case in the present disclosure, the test chemical is adapted to perform at least one detection reaction when the analyte is present in the body fluid, wherein the extent and/or the degree of the detection reaction typically depends on the concentration of the analyte. Generally, the test chemical may be adapted to perform a detection reaction in the presence of the analyte, wherein at least one detectable property of at least one of the body fluid and the test chemical is changed due to the detection reaction. The at least one detectable property generally may be selected from a physical property and a chemical property. In the following, without restricting potential other embodiments, reference will mainly be made to detection reactions in which one or more physical properties are changed due to the detection reaction, such as one or more of at least one electrical property and at least one optical property. Further, without restricting alternative solutions, reference will be made to detection reactions in which at least one chemical property which is optically detectable is changed, i.e., to optical test elements. Other test elements, such as combined optical and electrical test elements, however, are usable, too.
One technical challenge in typical analyte measurement systems using a measurement device and a test element, also referred to as a test carrier, resides in an accurate and precise positioning of the test element, in particular of the test field of the test element. Specifically in optical measurement systems, and also in many electrochemical measurement systems or measurement systems using both optical and electrochemical measurements, the test field has to be aligned precisely within a measurement device. Thus, as an example, in optical measurement systems, an optical area of the test element, such as an optical test field, and the optical detection system of the analytical device, which is also often referred to as a meter, have to be aligned. For this purpose, several technologies are known, such as the use of alignment pins or the use of electrical connectors of the measurement device for positioning purposes. Still, specifically in case electrical connectors are used for positioning, the precision of alignment remains to be an issue.
Despite the advantages achieved by the above-mentioned prior art technologies, several technical challenges remain. Thus, as an example, test elements are known which make use of both optical and electrochemical measurement principles. In case both of these detection methods are used, the test carrier typically has to be aligned precisely with respect to the optical detection system and, further, has to be electrically coupled to an electrical connector. Simultaneously achieving and fulfilling these requirements and targets, however, often imposes some severe design constraints. In many cases, electrical connectors having desired tolerances are not available. The fixation of the test element at two different positions, such as by using an alignment pin and an electrical connector, causes and over determination of the fixation which, often, suffers from insufficient tolerances of the alignment elements.
Further, in some systems, a closing of the test element receptacle and fixation of the test element within the test element receptacle is initiated by the test element itself, acting on a lever or the like. In these systems, the test element may be bent due to forces acting on the test element in a longitudinal direction which may lead to a misalignment of the test element. In other systems, separating the insertion of the test element and the clamping or fixation of the test element, a time delay may occur in between the insertion and the fixation, during which a misalignment may occur. Specifically in case a user is moving with a handheld system, there is a high risk for mechanical shocks or movements in between the insertion of the test strip and the closing of the measurement device. In this case, the test element, now being misaligned, may even be destroyed by the subsequent closing of the test element receptacle of the measurement device.
A further challenge resides in the fact that the test element, during use, has to be secured against external forces. Thus, as an example, a user may try to pull out a test strip during measurement or in other situations in which the test strip is fixed within the measurement device.